Exploring the Fundamental Components of a Synthesizer

Introduction

Hi. I am Darran Kelinske from Austin, TX in the USA. This lesson is for Week 6 of Introduction To Music Production at Coursera.org. This week I will be teaching you about the basic components of a Synthesizer which include the following: Oscillator, Filter, Amplifier, Envelope, and LFO. In this lesson, we will be exploring the components from a subtractive synthesis perspective.

Oscillator

The Oscillator, sometimes referred to as a Voltage Controlled Oscillator (VCO), is responsible for generating the raw audio signal. The timbre/personality of the raw sound can be modified by changing the waveform that is responsible for generating the audio signal. Most Oscillators allow you to select from sine, square, saw, and other kinds of waveforms. Some synthesizers, such as Native Instruments Massive, include a plethora of waveforms to choose from (see below).

The Oscillator will also typically allow you to modify the base frequency at which the waveform is generated. This allows you to modify the overall base pitch of the audio signal. As we can see in the Oscillator image below, the pitch has been lowered 12 semitones which results in an overall frequency reduction of the signal generated by the Oscillator.

Filter

The Filter, sometimes referred to as a Voltage Controlled Filter (VCF), is responsible for shaping the sound of the raw audio signal. This is typically achieved by setting the type of filter to be applied, the cutoff frequency, and the resonance.

Filter Types:

Many synthesizers allow you to choose from High-pass, Low-pass, Band-pass, and other filter types, but in subtractive synthesis the most common filter type to use is a low pass filter. Because the sound generated by the oscillator is so “bright”, we use a low-pass filter to remove/attenuate the partials that are above the cut-off frequency.

Cutoff Frequency:

The Cutoff Frequency is used by the filter to set the frequency at which the filter will begin attenuating the audio signal.

Resonance:

Resonance amplifies the signal at the specified cutoff frequency. As you modify the cutoff frequency, a high resonant filter will highlight the cut off frequency. This can most often be heard during filter sweeps in which the cutoff frequency can be heard sweeping across the audio signal.

An example of a Synthesizer filter from Massive:

Amplifier

The Amplifier, sometimes referred to as a Voltage Controlled Amplifier, is responsible for boosting the signal before passing it to an external source.

Envelope

An Envelope is used to modulate the signal that is passing through the Synthesizer. Typically, the Envelope is used to modulate the amplifier. A standard Envelope has four sections which include Attack Time, Decay Time, Sustain Level, and Release Time.

Attack Time

The attack time is how long it takes for the audio signal to go from nil to its peak. This time begins when the key is first pressed. Short attack times can create punchy sounds, while longer attack times can result in a sound that gradually builds when the key is pressed.

Decay Time

Decay time is how long it takes for the audio signal to decrease from it’s peak level to it’s sustain level. This is measured from the end of the attack time.

Sustain Level

The Sustain level begins after the attack and decay time and is the level in which the sound is maintained while the key is pressed.

Release Time

Lastly, the Release time is how long it takes for the audio signal to decrease from it’s sustain level to zero. Longer release times can create sounds will continue to persist after the key has been released.

A visualization of an “ADSR” Envelope in Massive is shown below.

LFO

An LFO (Low-Frequency Oscillator) is a modulation device that can be used to control other synthesizer components. For example, the LFO can be applied to the Oscillator so that the pitch oscillates between two frequencies. Similar to the Oscillator mentioned earlier, we can specify the type of waveform that is used by the Oscillator. We can also set the amount of oscillation that the LFO provides. Setting higher amounts will create sounds that waver in pitch.

Reflection

In this post, we reviewed the fundamental components of a Synthesizer. Further discussion of each of these components can be found in the manuals for some synthesizers as well as Wikipedia.

While this lesson is very basic, many of the ideas and facts covered in this lesson were new to me.

If there are any inaccuracies or if there is any feedback you have to provide, please contact me through Coursera or social media. Thank you for reading.